As is known in the field of orthopedic surgery, and more specifically spinal surgery, orthopedic fasteners may be used for fixation or for the anchoring of orthopedic devices or instruments to bone tissue. An exemplary use of fasteners may include using the fastener to anchor an orthopedic device, such as a bone plate, a spinal rod or a spinal spacer to a vertebral body for the treatment of a deformity or defect in a patient's spine. Focusing on the bone plate example, fasteners can be secured to a number of vertebral bodies and a bone plate can be connected to the vertebral bodies via the bone anchors to fuse a segment of the spine. In another example, orthopedic fasteners can be used to fix the location of a spinal spacer once the spacer is implanted between adjacent vertebral bodies. In yet another example, fasteners can be anchored to a number of vertebral bodies to fasten a spinal rod in place along a spinal column to treat a spinal deformity.
However, the structure of spinal elements presents unique challenges to the use of orthopedic implants for supporting or immobilizing vertebral bodies. Among the challenges involved in supporting or fusing vertebral bodies is the effective installation of an orthopedic implant that will resist migration despite the rotational and translational forces placed upon the plate resulting from spinal loading and movement. Also, for certain implants, having low profile characteristics is beneficial in terms of patient comfort as well as anatomic compatibility.
Furthermore, over time, it has been found that as a result of the forces placed upon the orthopedic implants and fasteners resulting from the movement of the spine and/or bone deterioration, the orthopedic fasteners can begin to “back out” from their installed position eventually resulting in the fasteners disconnecting from the implant and the implant migrating from the area of treatment.
As such, there exists a need for a fastening system that provides for low profile placement of the bone anchor or screws and provides a mechanism where the fasteners are blocked to prevent the anchors from “backing out” of their installed position.